According to the
wiki these are in the cows raws:
[SELECT_CASTE:ALL]
[SET_TL_GROUP:BY_CATEGORY:ALL:
HAIR]
[TL_COLOR_MODIFIER:BLACK:1:BROWN:1:
WHITE:1:GRAY:1:LIGHT_BROWN:1:DARK_BROWN:1:TAN:1:AUBURN:1:CHESTNUT:1:SLATE_GRAY:1:
CREAM:1:CINNAMON:1:BUFF:1:
BEIGE:1:CHOCOLATE:1:CHARCOAL:1:ASH_GRAY:1:RUSSET:1:IVORY:1:FLAX:1:PUMPKIN:1:GOLD:1:GOLDEN_YELLOW:1:GOLDENROD:1:COPPER:1:SAFFRON:1:AMBER:1:MAHOGANY:1:
OCHRE:1:PALE_BROWN:1:RAW_UMBER:1:BURNT_SIENNA:1:BURNT_UMBER:1:SEPIA:1:DARK_TAN:1:PALE_CHESTNUT:1:DARK_CHESTNUT:1:TAUPE_PALE:1:TAUPE_DARK:1:
TAUPE_SANDY:1:TAUPE_GRAY:1:TAUPE_MEDIUM:1:ECRU:1]
[TLCM_NOUN:hair:SINGULAR]
[SET_TL_GROUP:BY_CATEGORY:ALL:
SKIN]
[TL_COLOR_MODIFIER:BROWN:1:BURNT_UMBER:1:CINNAMON:1:COPPER:1:DARK_BROWN:1:DARK_PEACH:1:
DARK_TAN:1:ECRU:1:PALE_BROWN:1:PALE_CHESTNUT:1:PALE_PINK:1:PEACH:1:PINK:1:RAW_UMBER:1:SEPIA:1:TAN:1:
TAUPE_PALE:1:TAUPE_SANDY:1]
[TLCM_NOUN:skin:SINGULAR]
What this means is that all cows and bulls will have one color, there will be no spotted cows. They can have white or cream-colored hair, but not skin. The closest is taupe_pale which is a brighter version of
this.. you can mod out all the skin colors except the one you want, or you can limit the selection fairly easy. If you want the cow to be able to have different-colored legs or such then you have to do more modding.